docs: def _verify(function):
      """decorator to ensure pin is properly set up"""
      # @functools.wraps
      def wrapped(pin, *args, **kwargs):
          pin = int(pin)
          if pin not in _open:
              ppath = gpiopath(pin)
              if not os.path.exists(ppath):
                  log.debug("Creating Pin {0}".format(pin))
                  with _export_lock:
                      with open(pjoin(gpio_root, 'export'), 'w') as f:
                          _write(f, pin)
              value = open(pjoin(ppath, 'value'), FMODE)
              direction = open(pjoin(ppath, 'direction'), FMODE)
              _open[pin] = PinState(value=value, direction=direction)
          return function(pin, *args, **kwargs)
      return wrapped